Process for preparing 3-[(4S)-8-bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-A][1,4]benzodiazepine-4-yl]propionic acid methyl ester or the benzene sulfonate salt thereof, and compounds useful in that process

ABSTRACT

The invention concerns a new process for preparing 3-[(4S)-8-bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-a][1,4]benzodiazepine-4-yl]-propionic acid methyl ester 
                         
or
     3-[(4S)-8-bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-a][1,4]benzodiazepine-4-yl]propionic acid methyl ester benzene sulfonate (P)   which comprises reacting 3-[(S)-7-bromo-2-((R and/or S)-2-hydroxy-propylamino)-5-pyridin-2-yl-3H-benzo[e][1,4]diazepin-3-yl]-propionic acid methyl ester of formula (EM)   

                         
with an oxidizing agent and optionally treating the reaction product under acidic conditions, such as to produce the compound of formula (F) or the compound (P), and new compounds useful as starting materials or as intermediates for performing that process.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/841,899, filed Sep. 1, 2015, which is a divisional application ofU.S. application Ser. No. 13/496,742, filed Aug. 30, 2012, which is theU.S. National Stage of International Application No. PCT/EP2010/005668,filed Sep. 15, 2010 which designated the United States and has beenpublished as International Publication No. WO 2011/032692 and whichclaims the priority of European Patent Application, Serial No.09011914.0 filed Sep. 18, 2009, pursuant to 35 U.S.C. 119(a)-(d).

BACKGROUND OF THE INVENTION

The present invention relates to a process for preparing3-[(4S)-8-bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-a][1,4]benzodiazepine-4-yl]-propionicacid methyl ester and the benzene sulfonate salt thereof, starting from3-[(S)-7-Bromo-2-((R and/orS)-2-hydroxy-propylamino)-5-pyridin-2-yl-3H-benzo[e][1,4]diazepin-3-yl]-propionicacid methyl ester or3-[(S)-7-Bromo-2-((R)-2-hydroxy-propylamino)-5-pyridin-2-yl-3H-benzo[e][1,4]diazepin-3-yl]-propionicacid methyl ester, and new compounds useful as starting material orintermediate in that process.

WO 00/69836 describes short-acting benzodiazepines that include acarboxylic ester moiety and are inactivated by non-specific tissueesterases. An organ-independent elimination mechanism is predicted to becharacteristic of these benzodiazepines, providing a more predictableand reproducible pharmacodynamic profile. The compounds are suitable fortherapeutic purposes, including sedative-hypnotic, anxiolytic, musclerelaxant and anticonvulsant purposes. The compounds are short-acting CNSdepressants that are useful to be administered intravenously in thefollowing clinical settings: preoperative sedation, anxiolysis, andamnestic use for perioperative events; conscious sedation during shortdiagnostic, operative or endoscopic procedures; as a component for theinduction and maintenance of general anesthesia, prior and/orconcomitant to the administration of other anaesthetic or analgesicagents; ICU sedation.

One of the compounds disclosed in that document is3-[(4S)-8-bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-a][1,4]benzodiazepine-4-yl]-propionicacid methyl ester of formula (F) below

WO 00/69836 teaches a process for preparing the above compound offormula (F), which comprises:

(a) preparing3-[(S)-7-bromo-2-oxo-5-pyridin-2-yl-2,3-dihydro-1H-1,4-benzodiazepin-3-yl]-propionicacid methyl ester of formula (D)

by reacting (2-amino-5-bromo-phenyl)-pyridin-2-yl-methanone of formula(A)

in chloroform with an alpha-Fmoc-protected-amino acid chloride (obtainedby reacting FMOC-Glu(OMe)-OH and oxalylchloride in dichloromethane),treating the obtained amide with triethylamine in dichloromethane, thenwith acetic acid in 1,2-dichloroethane,isolating the compound of formula (D), and(b) reacting the compound of formula (D) with a suspension of sodiumhydride in THF, treating the reaction mixture withbis-morpholinophosphochloridate (BPMC) in THF, filtering the reactionmixture, reacting the filtrate with DL-1-amino-propanol, purifying thealcoholic adduct obtained, treating that purified alcoholic adduct witha mixture of DMSO and oxalyl chloride in dichloromethane, treating thereaction mixture with triethylamine, diluting with ethyl acetate,washing with aqueous solutions and concentrating to give a foam,treating that foam with a catalytic amount of p-toluenesulfonic acid,neutralizing the solution with sodium hydrogenocarbonate and isolatingthe compound of formula (F).

WO 2008/007071 discloses a method of preparing the besylate salt (P) ofthe above compound of formula (F) by adding benzene sulfonic acid to asolution of that compound in toluene or ethyl acetate, stirring,filtering, washing with toluene or ethyl acetate and drying undervacuum. That method yields3-[(4S)-8-Bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-a][1,4]benzodiazepine-4-yl]propionicacid methyl ester benzene sulfonate (P) which is taught to be aparticularly interesting active pharmaceutical ingredient (API).

The process for preparing the direct precursor of that API, namely3-[(4S)-8-bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-a][1,4]benzodiazepine-4-yl]propionicacid methyl ester of formula (F), or that API,3-[(4S)-8-Bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-a][1,4]benzodiazepine-4-yl]propionicacid methyl ester benzene sulfonate (P), starting from the compound offormula (A) disclosed in WO 00/69836 is not satisfying for an industrialpreparation, notably because of the high number of steps, the lowoverall yield and the insufficient optical purity of the compoundsobtained at the different steps.

The objective of the invention is to find a process for preparingcompound (P) and precursors thereof that does not have the abovedrawbacks.

That objective is attained by the invention as defined in the appendedclaims.

SUMMARY OF THE INVENTION

The process of the invention thus relates to a new method for preparingthe compound of formula (F) or its besylate salt (P), comprisingoxidizing 3-[(S)-7-bromo-2-((R and/orS)-2-hydroxy-propylamino)-5-pyridin-2-yl-3H-benzo[e][1,4]diazepin-3-yl]-propionicacid methyl ester of formula (EM)

or in a preferred embodiment oxidizing3-[(S)-7-bromo-2-((R)-2-hydroxy-propylamino)-5-pyridin-2-yl-3H-benzo[e][1,4]diazepin-3-yl]-propionicacid methyl ester of formula (E)

That method allows to obtain3-[(4S)-8-bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-a][1,4]benzodiazepine-4-yl]propionicacid methyl ester of formula (F) or its besylate salt (P), namely3-[(4S)-8-Bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-a][1,4]benzodiazepine-4-yl]propionicacid methyl ester benzene sulfonate, with very high chemical and chiralpurities.

The process of the invention may include steps for preparing3-[(S)-7-bromo-2-((R and/orS)-2-hydroxy-propylamino)-5-pyridin-2-yl-3H-benzo[e][1,4]diazepin-3-yl]-propionicacid methyl ester of formula (EM) starting from one of the precursors ofthe compound of formula (F) disclosed in WO 00/69836, namely3-[(S)-7-bromo-2-oxo-5-pyridin-2-yl-2,3-dihydro-1H-1,4-benzodiazepin-3-yl]-propionicacid methyl ester of formula (D) or(2-amino-5-bromo-phenyl)-pyridin-2-yl-methanone of formula (A).

It then provides a process for preparing3-[(4S)-8-bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-a][1,4]benzodiazepine-4-yl]propionicacid methyl ester of formula (F) or3-[(4S)-8-Bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-a][1,4]benzodiazepine-4-yl]propionicacid methyl ester benzene sulfonate (P), with very high chemical andchiral purities, which has less steps, a better reproducibility and abetter overall yield with regard to the compound of formula (D) or thecompound of formula (A) than the process disclosed in WO 00/69836.

The invention concerns a process for preparing3-[(4S)-8-bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-a][1,4]benzodiazepine-4-yl]propionicacid methyl ester of formula (F)

which comprises reacting 3-[(S)-7-bromo-2-((R and/orS)-2-hydroxy-propylamino)-5-pyridin-2-yl-3H-benzo[e][1,4]diazepin-3-yl]-propionicacid methyl ester of formula (EM)

with an oxidizing agent and optionally treating the reaction productunder acidic conditions, such as to produce the compound of formula (F).

The compound of formula (EM) may be3-[(S)-7-bromo-2-((R)-2-hydroxy-propylamino)-5-pyridin-2-yl-3H-benzo[e][1,4]diazepin-3-yl]-propionicacid methyl ester of formula (E)

3-[(S)-7-bromo-2-((S)-2-hydroxy-propylamino)-5-pyridin-2-yl-3H-benzo[e][1,4]diazepin-3-yl]-propionicacid methyl ester of formula (E′)

or a mixture of the compounds of formula (E) and (E′).

Preferably the compound of formula (EM) is a compound of formula (E).

The compound of the formula (EM) can be obtained by reacting in anaprotic solvent the compound of formula (E1) with (R)-1-amino-2-propanolor (S)-1-amino-2-propanol, both compounds are commercially available.

In one embodiment in step (b) the compound of formula (E1) can bereacted with (S)-1-amino-2-propanol, yielding3-[(S)-7-bromo-2-((S)-2-hydroxy-propylamino)-5-pyridin-2-yl-3H-benzo[e][1,4]diazepin-3-yl]-propionicacid methyl ester of formula (E′).

Preferably in step (b) the compound of formula (E1) is reacted with(R)-1-amino-2-propanol, yielding the preferred3-[(S)-7-bromo-2-((R)-2-hydroxy-propylamino)-5-pyridin-2-yl-3H-benzo[e][1,4]diazepin-3-yl]-propionicacid methyl ester of formula (E).

The optical purity of the compounds of formula (E) and (E′) depends onthe purity of the 1-amino-2-propanol used in the synthesis. For thepurposes of the present invention it is preferred to obtain the compoundof the formula (E) at an optical purity of ≥95%, preferably ≥99%, andmore preferably ≥99.5%, using (R)-1-amino-2-propanol.

The oxidizing agent is an agent apt to oxidize a secondary alcohol to aketone without reacting with the other reactive groups of the compoundof formula (EM).

Examples of suitable oxidizing agents are sulfonated pyridine indimethylsulfoxide (DMSO) in presence of a base such asdiisopropylethylamine (DIEA), oxalyl chloride in DMSO in presence of abase such as triethylamine, Albright-Goldman oxidation reagent (aceticacid anhydride/DMSO), S-IBX oxidation reagent(1-Hydroxy-(1H)-benzo-1,2-iodoxol-3-one-1-oxide), a combination ofhypochlorite and a catalytic amount of tetramethylpiperidine-1-oxyl(TEMPO), and a hypervalent iodine compound of formula (DM)

wherein R1 is acyl, preferably C₂-C₁₀ acyl, more preferably C₂-C₄ acyl,such as 1,1,1-triacetoxy-1,1-dihydro-1,2-benziodoxol-3(1H)-one(Dess-Martin periodinane).

The oxidizing agent may convert the compound of formula (EM) directly tothe compound of formula (F), or to the intermediate ketone of formula

which can then be cyclized under acidic conditions into the compound offormula (F).

The compound of formula (F) may be isolated by methods routinely used inthe art of synthetic organic chemistry, which may e.g. includeevaporating the solvent under vacuum, dissolving the residue in asuitable solvent, filtering, washing with different aqueous solutionsand re-extracting the combined aqueous solutions with a suitablesolvent.

For the purposes of the present invention it is preferred to obtain thecompound of the formula (F) at an optical purity of ≥95%, preferably≥99%, more preferably ≥99.5%, and most preferably >99.9%.

A preferred oxidizing agent is an hypervalent iodine compound of formula(DM)

wherein R1 is acyl, preferably C₂-C₁₀ acyl, in particular C₂-C₄ acyl.

Most preferably R1 is acetyl, the compound of formula (DM) then being1,1,1-triacetoxy-1,1-dihydro-1,2-benzoiodoxol-3(1H)-one) (Dess-Martinperiodinane).

Where the oxidizing agent is Dess-Martin periodinane, the reaction isgenerally performed by treating the compound of formula (EM) with astoichiometric excess, usually from 1.0 to 2.0, preferably 1.2 to 1.8,particularly 1.4 to 1.6 equivalent of Dess-Martin periodinane, in anaprotic solvent such as e.g. dichloromethane, chloroform, acetonitrile,tetrahydrofuran or butanone. Particularly good results have beenobtained in butanone.

The Dess-Martin periodinane is conveniently added in solid form and inportions to a solution of the compound of formula (EM) in an aproticsolvent.

Where the aprotic solvent is butanone, the reaction is preferablycarried out at a temperature between 30 and 45° C.

Where the oxidizing agent is Dess-Martin periodinane, the reactionproduct mainly contains the compound of formula (F) and there isgenerally no further acidic reaction performed.

The compound of formula (F) may be isolated by methods routinely used inthe art of synthetic organic chemistry, which may e.g. includeevaporating the solvent under vacuum, dissolving the residue in asuitable solvent, filtering, washing with different aqueous solutionsand re-extracting the combined aqueous solutions with a suitablesolvent.

Another interesting oxidizing agent is a combination of a catalyticamount of tetramethylpiperidine-1-oxyl (TEMPO) and hypochlorite.

The compound of formula (EM) is generally treated in solution with acatalytic amount of TEMPO, e.g. 0.005 to 0.03 equivalent of TEMPO, and1.0 to 1.8 equivalent of hypochlorite, usually in a solvent or a solventmixture which contains water having a pH 6.0 to 8.0, the pH beingadjusted if necessary by adding additives such as e.g. hydrogencarbonate or acetic acid, and a salt such as sodium or potassiumbromide. A suitable solvent mixture is e.g. ethyl acetate/toluene/wateror dichloromethane/water.

Where the oxidizing agent is a combination of a catalytic amount ofTEMPO and hypochlorite, the reaction product mainly contains3-[(S)-7-bromo-2-(2-oxo-propylamino)-5-pyridin-2-yl-3H-1,4-benzodiazepin-3-yl]-propionicacid methyl ester of formula (FK)

That compound can be cyclized into the compound of formula (F) underacidic conditions.

Suitable acidic conditions are generally an organic acid in an organicsolvent.

Examples of suitable acidic conditions are p-toluene sulfonic acid inchloroform or a mixture of benzene sulfonic acid in substantially lessthan the stoichiometric amount (preferably less than a fifth of thestoichiometric amount, more preferably about a tenth of thestoichiometric amount) and molecular sieve MS3A in dichloromethane.

The compound of formula (F) may be isolated by methods routinely used inthe art of synthetic organic chemistry, which may e.g. includeevaporating the solvent under vacuum, dissolving the residue in asuitable solvent, filtering, washing with different aqueous solutionsand re-extracting the combined aqueous solutions with a suitablesolvent.

The invention also concerns a process for preparing the besylate salt3-[(4S)-8-bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-a][1,4]benzodiazepine-4-yl]propionicacid methyl ester benzene sulfonate (P) which comprises

(a) reacting 3-[(S)-7-bromo-2-((R and/orS)-2-hydroxy-propylamino)-5-pyridin-2-yl-3H-benzo[e][1,4]diazepin-3-yl]-propionicacid methyl ester of formula (EM)

with an oxidizing agent, and(b) treating the reaction product obtained in step (a) with benzenesulfonic in an organic solvent or an organic solvent mixture, such as toproduce the compound (P).

The compound (P) may be isolated by methods routinely used in the art ofsynthetic organic chemistry, which may e.g. include crystallisation ofthe besylate salt.

For the purposes of the present invention it is preferred to obtain thecompound of the formula (P) at an optical purity of ≥95%, preferably≥99%, more preferably ≥99.5%, and most preferably >99.9%.

Preferably the compound of formula (EM) is a compound of formula (E).

In a preferred embodiment the oxidation agent is a combination ofhypochlorite and a catalytic amount of TEMPO, whereby the compound offormula (EM) is treated in solution with 0.005 to 0.03 equivalent ofTEMPO and 1.0 to 1.8 equivalent of hypochlorite, such as to give3-[(S)-7-bromo-2-(2-oxo-propylamino)-5-pyridin-2-yl-3H-1,4-benzodiazepin-3-yl]-propionicacid methyl ester of formula (FK)

and(b) treating the compound of formula (FK) with benzene sulfonic acid inan organic solvent or an organic solvent mixture, such as to produce thecompound (P).

The organic solvent or the organic solvent mixture used in step (b) isan organic solvent capable of favouring in presence of benzene sulfonicacid the cyclization of the3-[(S)-7-bromo-2-(2-oxo-propylamino)-5-pyridin-2-yl-3H-1,4-benzodiazepin-3-yl]-propionicacid methyl ester of formula (FK), the formation of the benzenesulfonate salt and optionally the crystallisation of that salt.

Examples of suitable organic solvent mixtures are ethyl acetate andethanol, ethyl acetate and 2-propanol, and ethyl acetate and methanol.

A preferred organic solvent mixture is ethyl acetate and ethanol.

3-[(S)-7-bromo-2-((R and/orS)-2-hydroxy-propylamino)-5-pyridin-2-yl-3H-benzo[e][1,4]diazepin-3-yl]-propionicacid methyl ester of formula (EM) used as starting material in the abovedefined process for preparing3-[(4S)-8-bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-a][1,4]benzodiazepine-4-yl]propionicacid methyl ester of formula (F) or3-[(4S)-8-bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-a][1,4]benzodiazepine-4-yl]propionicacid methyl ester benzene sulfonate (P), may be prepared by a methodcomprising

(a) reacting3-[(S)-7-bromo-2-oxo-5-pyridin-2-yl-2,3-dihydro-1H-1,4-benzodiazepin-3-yl]-propionicacid methyl ester of formula (D)

with lithium diisopropylamide (LDA) andbis-morpholinophosphorylchloridate (BMPC), such as to give the compoundof formula (E1),

and(b) reacting the compound of formula (E1) with (R)-1-amino-2-propanol or(S)-1-amino-2-propanol.

Step (a) is generally performed by dissolving the compound of formula(D) in an aprotic solvent and adding LDA and BMPC. Usually LDA is addedprior to BMPC. The skilled person would also consider adding BMPC priorto LDA as being a suitable alternative.

A suitable aprotic solvent is for instance tetrahydrofurane (THF), amixture of THF with an alkane solvent (e.g. heptane) and an aralkanesolvent (e.g. ethylbenzene), or an ether, e.g. diethyl ether.

Generally 1.0 to 1.5 equivalent of LDA and at least 1.5 equivalents ofBMPC are used.

Preferably 1.0 to 1.2, in particular 1.0 to 1.1, equivalent of LDA andat least 2.0 equivalents of BMPC are used.

Step (b) is generally carried out by reacting in an aprotic solvent thecompound of formula (E1) with (R)-1-amino-2-propanol or(S)-1-amino-2-propanol to yield the compound of the formula (EM).

In one embodiment in step (b) the compound of formula (E1) can bereacted with (S)-1-amino-2-propanol, yielding3-[(S)-7-bromo-2-((S)-2-hydroxy-propylamino)-5-pyridin-2-yl-3H-benzo[e][1,4]diazepin-3-yl]-propionicacid methyl ester of formula (E′).

Preferably in step (b) the compound of formula (E1) is reacted with(R)-1-amino-2-propanol, yielding the preferred3-[(S)-7-bromo-2-((R)-2-hydroxy-propylamino)-5-pyridin-2-yl-3H-benzo[e][1,4]diazepin-3-yl]-propionicacid methyl ester of formula (E).

An example of a suitable aprotic solvent is THF, a mixture of THF withan alkane solvent (e.g. heptane) and an aralkane solvent (e.g.ethylbenzene), or an ether, e.g. ethyl ether.

3-[(S)-7-bromo-2-((R)-2-hydroxy-propylamino)-5-pyridin-2-yl-3H-benzo[e][1,4]diazepin-3-yl]-propionicacid methyl ester of formula (EM) is usually isolated and purified byrecrystallisation from a suitable solvent, preferably one selected fromthe group of ethyl acetate, isobutylacetate, 2-propanol, toluene, orethyl acetate/heptane.

3-[(S)-7-bromo-2-oxo-5-pyridin-2-yl-2,3-dihydro-1H-1,4-benzodiazepin-3-yl]-propionicacid methyl ester of formula (D) used above as starting material forpreparing3-[(S)-7-bromo-2-((R)-2-hydroxy-propylamino)-5-pyridin-2-yl-3H-benzo[e][1,4]diazepin-3-yl]-propionicacid methyl ester of formula (EM), may be prepared by a methodcomprising cyclizing the compound of formula (C)

by treatment with a base in an organic solvent or organic solventmixture.

A suitable organic solvent is for instance THF, DMF, acetonitrile ormethanol.

A suitable base is for instance an alkaline metal hydrogen carbonate,e.g. sodium hydrogen carbonate, or a tertiary amine, e.g. triethylamine,diisopropylethylamine, N,N-dimethylaniline and pyridine.

3-[(S)-7-bromo-2-oxo-5-pyridin-2-yl-2,3-dihydro-1H-1,4-benzodiazepin-3-yl]-propionicacid methyl ester of formula (D) may be purified by recrystallisationfrom a secondary alcoholic solvent, e.g. isopropanol or isobutanol,preferably isopropanol, or a solvent mixture such as e.g. ethylacetate/heptane.

The compound of formula (C) used above as starting material forpreparing3-[(S)-7-bromo-2-oxo-5-pyridin-2-yl-2,3-dihydro-1H-1,4-benzodiazepin-3-yl]-propionicacid methyl ester of formula (D), may be prepared by cleaving the^(t)Boc group of the compound of formula (B)

by treatment with hydrogen chloride.

The reaction may be performed by dissolving the compound of formula (B)in a polar solvent such as ethanol or methanol, adding hydrogen chloridein 1,4-dioxane and preferably cooling the reaction mixture.

The compound of formula (B) used above as starting material forpreparing the compound of formula (C) may be prepared by treating(2-amino-5-bromo-phenyl)-pyridin-2-yl-methanone of formula (A)

with tBoc-Glu(OMe)-OH in an organic solvent in presence of a couplingagent.

A suitable organic solvent is for instance THF, DMF, dichloromethane orethyl acetate.

Suitable coupling agents include those selected from the groupconsisting of Dicyclohexylcarbodiimide (DCC),N,N,N′,N′-Tetramethyl-O-(7-azabenzotriazol-1-yl)uroniumhexafluorophosphate (HATU),2-(1H-Benzotriazole-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate(HBTU), 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC), propanephosphonic acid anhydride T3P,Benzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphatePyBOP, isobutylchloroformate, carbonyldiimidazole (CDI), chlorenamine,or N,N′-diisopropylcarbodiimide (DIC).

Depending on the coupling agent, a base such as e.g.diisopropylethylamine (DIEA), triethylamine (TEA) or N-methylmorpholine(NMM), or another additive may be used.

A preferred coupling agent is DCC, e.g. in dichloromethane ordimethylformamide (DMF).

The invention also concerns a new compound useful as starting materialor intermediate for performing the above defined process for preparing3-[(4S)-8-bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-a][1,4]benzodiazepine-4-yl]propionicacid methyl ester of formula (F) or3-[(4S)-8-bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-a][1,4]benzodiazepine-4-yl]propionicacid methyl ester benzene sulfonate (P), which is selected from thegroup consisting of

(a) 3-[(S)-7-Bromo-2-((R)-2-hydroxy-propylamino)-5-pyridin-2-yl-3Hbenzo[e][1,4]diazepin-3-yl]-propionic acid methyl ester of formula (E)

b)3-[(S)-7-Bromo-2-(2-oxo-propylamino)-5-pyridin-2-yl-3H-1,4-benzodiazepin-3-yl]-propionicacid methyl ester of formula (FK)

c) the compound of formula (E1)

d) the compound of formula (C)

ore) the compound of formula (B)

The invention also relates to the use of the compounds of the formula(EM), (E), (E1), (FK), (C), (B) in the preparation of a compound of theformula (F) or its besylate salt (P), and also the use of the abovedefined process for preparing3-[(4S)-8-bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-a][1,4]benzodiazepine-4-yl]propionicacid methyl ester of formula (F), in the preparation of3-[(4S)-8-bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-a][1,4]benzodiazepine-4-yl]propionicacid methyl ester benzene sulfonate (P), whereby the3-[(4S)-8-bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-a][1,4]benzodiazepine-4-yl]propionicacid methyl ester of formula (F) is treated with benzene sulfonic acidin a solvent or a solvent mixture, preferably selected from the groupconsisting of ethanol, 2-propanol, ethanol/ethyl acetate,2-propanol/ethyl acetate and methanol/ethyl acetate. The formed besylatesalt (P) is then optionally crystallized from that solvent or solventmixture.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following examples illustrate the invention.

Example A1

Preparation of the Compound of Formula (B)

222 g (801 mmol) (2-amino-5-bromo-phenyl)-pyridin-2-yl-methanone offormula (A)

(prepared as described in European Journal of Organic Chemistry, 2006,13, 2987-2990) and 230 g (881 mmol) tBoc-Glu(OMe)-OH were mixed assolids and dissolved in 1200 ml dichloromethane and the solution wascooled to a temperature of −10° C. A solution of coupling reagentdicyclohexylcarbodiimide DCC (165 g, 801 mmol) in 400 ml dichloromethanewas added dropwise over a period of 1 hour while the internaltemperature was kept at a temperature from −1000 to −5° C., then thesolution was stirred for 40 hours at a temperature of −5° C. to 0° C.The suspension was filtered, the filter cake was washed with 1000 mldichloromethane and the filtrate was evaporated to a yellow residue,showing for the main product the following NMR data:

1H-NMR (CDCl3, 300 MHz) 11.29 (brs, 1H); 8.65 (dt, 1H, J=4.8, 1.4); 8.50(d, 1H, J=9.0); 7.91 (d, 1H, J=2.3); 7.86 (m, 2H); 7.59 (dd, 1H, J=9.0,2.3) 7.45 (ddd, 1H, J=6.4, 4.0, 2.3); 5.27 (brd, 1H, J=6.4); 4.27 (brm,1H); 3.60 (s, 3H); 2.52-2.14 (m, 2H); 2.04-1.82 (m, 2H); 1.36 (s, 9H),corresponding to the compound of formula (B).

Example A2

Preparation of the Compound of Formula (C)

The compound of formula (B) (1833 g, 2642 mmol) was dissolved in 2200 mlmethanol at room temperature. The solution was transferred into a 10 lreactor and cooled to a temperature below 20° C. To this solutionhydrogen chloride (11200 mmol) in 2800 ml 1,4-dioxane was added over aperiod of 15 minutes while maintaining the reaction mixture at atemperature of 15 to 10° C. The mixture was stirred for 3 hours at atemperature of 15 to 10° C. The solution obtained was directly used inExample A3 below. That solution showed for the main product thefollowing NMR data:

1H-NMR (CDCl3, 300 MHz) 11.23 (brs, 1H); 8.63 (dt, 1H, J=4.6, 1.3); 8.36(brd, 2H, J=4.3); 8.06 (d, 1H, J=1.3); 8.0 (m, 1H); 7.78 (dd, 1H, J=8.6,2.4) 7.64 (m, 2H) 7.46 (d, 1H, 8.6); 4.00 (brm, 1H); 3.62 (s, 3H);2.41-2.23 (m, 2H); 1.83-1.56 (m, 2H), corresponding to the compound offormula (C).

Example A3

Preparation of3-[(S)-7-bromo-2-oxo-5-pyridin-2-yl-2,3-dihydro-1H-1,4-benzodiazepin-3-yl]-propionicacid methyl ester of formula (D)

449 g (5343 mmol) of sodium hydrogen carbonate were suspended in 2000 mlof acetonitrile under vigorous stirring. The solution of the compound offormula (C) obtained in Example A2 above (1743 g, 763 mmol) was added tothat suspension in 4 equal portions at room temperature over a period of30 minutes (actual solvent ratio methanol/1,4-dioxane/acetonitrile:3/4/10). The temperature decreased to 15° C., with an intensive gasdevelopment and a slight foaming after addition of each portion. Thecolour switched after each addition from orange (colour of thehydrochloric solution) to yellow-green. The yellow-green solution wasstirred at a temperature of about 15° C. for 3 hours 40 minutes. Thereaction mixture was filtered over a thin layer of celite, washed withacetonitrile and evaporated in vacuo at 50° C. bath temperature,yielding 424 g of viscous resin, The resin was dissolved in 1500 ml of2-propanol at 85° C. After cooling the precipitated solid was isolatedby filtration and washed with 2-propanol and dried at a temperature of35° C. in vacuo to give the product as a yellow crystalline solid (215.8g, 528 mmol) having the following NMR data:

1H-NMR (CDCl3, 300 MHz) 8.69 (s, 1H); 8.52 (dq, 1H, J=4.8, 1.6, 0.8);7.99 (dt, 1H, J=8.0, 1.0); 7.73 (td, 1H J=7.8, 1.8); 7.54-7.43 (m, 2H)7.28 (qd, 1H, J=7.6, 4.8, 1.0); 6.93 (d, 1H, J=8.6); 3.67 (dd, 1H J=7.6,6.1); 3.60 (s, 3H) 2.66-2.34 (m, 4H), corresponding to the compound offormula (D).

For the process described in Examples A1 to A3, the overall yield from(2-amino-5-bromo-phenyl)-pyridin-2-yl-methanone of formula (A) to3-[(S)-7-bromo-2-oxo-5-pyridin-2-yl-2,3-dihydro-1H-1,4-benzodiazepin-3-yl]-propionicacid methyl ester of formula (D) is about 67%. The chemical purity ofthe isolated solid as determined by HPLC (at 230 nm) was 98.35% and itsoptical (chiral) purity determined by HPLC (at 290 nm) was 100%.

Example A4

Preparation of3-[(S)-7-bromo-2-oxo-5-pyridin-2-yl-2,3-dihydro-1H-1,4-benzodiazepin-3-yl]-propionicacid methyl ester of formula (E)

1.36 kg (3.39 mol) compound of formula (D) was suspended in 3500 ml drytetrahydrofurane (THF) under argon and cooled down to −18° C. A 2Msolution of lithium diisopropylamide LDA (3.4 mol) in 1700 mlTHF/heptane/ethylbenzene was added over a period of 90 minutes. Theaddition was exothermic and the temperature was controlled to be between−10 and −5° C. The mixture was then stirred for 105 minutes at 0° C.,followed by the portionwise addition ofbis-morpholinophosphoryl-chloridate BMPC (1.74 kg; 6.78 mol) over 15minutes. The brown suspension was stirred for 150 minutes and thetemperature held between −5 and 0° C. An analytical amount of the mainproduct isolated by chromatography was found to have the following NMRdata:

1H-NMR (CDCl3, 300 MHz) 8.68 (ddd, 1H, J=4.8, 1.7, 0.9); 7.96 (dt, 1H,J=7.9, 1.0); 7.8 (td, 1H, J=7.7, 1.8); 7.67 (dd, 1H, J=8.6, 2.3); 7.57(d, 1H, J=2.0); 7.41 (ddd, 1H, J=7.5, 4.8, 1.2); 7.36 (d, 1H, J=8.6);7.2 (m, 1H); 3.85-3.65 (m, 8H+3H) 3.33-3.19 (m, 8H); 2.76-2.45 (m, 4H),corresponding to the compound of formula (E1)

A solution of (R)-1-amino-2-propanol (519 g; 6.91 mol) in dry THF (1500ml) was added within 105 minutes and the temperature was kept between +4and −2° C. The mixture was stirred for 16 hours at room temperature. Asecond addition of the (R)-1-amino-2-propanol (102 g; 1.36 mol) in dryTHF (150 ml) was carried out within 5 minutes. It was stirred foranother 25 hours, then evaporated widely.

To the pasty residue were added dichloromethane (5 l) and saturatedaqueous sodium bicarbonate solution (5 l). The layers were separated.The organic layer was washed with saturated aqueous ammonium chloridesolution (2.5 l) and water (2 l). Each aqueous layer was re-extractedwith dichloromethane (200 ml). The combined organic layers were driedover sodium sulfate, filtered and evaporated. The crude product wasrecrystallised from 95° C. hot toluene after slow cooling and filtrationas a yellowish solid in 56% yield (876 g) with the following NMR data:

1H-NMR (CDCl3, 300 MHz) 8.6 (ddd, 1H, J=4.8, 1.6, 1.0); 7.87 (dm, 1H,J=7.8); 7.79 (td, 1H, J=7.5, 1.7); 7.51 (dd, 1H, J=8.7, 2.3); 7.39 (d,1H, J=2.3); 7.36 (ddd, 1H, J=7.4, 2.5, 1.4); 7.13 (d, 1H, J=8.8); 5.76(tb, 1H) 5.19 (b, 1H); 3.98 (m, 1H) 3.71 (s, 3H); 3.5-3.2 (m, 3H)2.9-2.3 (m, 4H); 1.17 (d, 3H, J=6.3), corresponding to the compound offormula (E). Chemical purity as determined by HPLC (254 nm) was 98.77%.The optical purity as determined by HPLC (290 nm) was 99.54%.

Example A5

Preparation of3-[(4S)-8-bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-a][1,4]benzodiazepine-4-yl]propionicacid methyl ester of formula (F) using Dess-Martin periodinane asoxidizing agent

The compound of formula (E) (874 g, 1.9 mol) was dissolved in butanone(7.8 l) and warmed to 30° C. Dess Martin periodinane (968 g; 2.28 mol)was added in portions. A short time after the addition of the firstamounts a solid formed being the unsoluble by-products of the reagent.The temperature of the reaction mixture had increased to 43° C. uponcomplete addition. This temperature was maintained for 45 minutes. DessMartin periodinane (242 g; 0.58 mol) was again added. Stirring wascontinued for 40 minutes. Then the volatiles were widely removed invacuo and the residue was diluted with ethyl acetate (10 l). The solidswere removed by filtration and washed with ethyl acetate (0.5 l). Thecombined filtrates of both runs were washed with saturated aqueoussodium bicarbonate solution (7 l) and saturated aqueous ammoniumchloride solution (7 l). The combined aqueous layers were re-extractedwith ethyl acetate (0.5 l). The combined organic layers were extractedthree times with 1 N hydorochloric acid (4 l, 2×2 l). The combinedaqueous layers was washed with ethyl acetate (100 ml). Ethyl acetate (7l) was added to the aqueous layer, followed by the slow addition of 1 Nsodium hydroxide solution (8 l) under vigorous stirring. At a pH between4 to 5 the product went into the organic layer as indicated by a colorswitch of the layers. After complete addition, the pH value was 9. Thelayers were separated and the aqueous extracted with ethyl acetate (1l). The combined organic layers were washed with water dried over sodiumsulfate, filtered and evaporated. The crude product was obtained as abrown resin (783 g, chemical purity by HPLC at 230 nm=93.91%, chiralpurity by HPLC (250 nm) is =98.47%) still containing 13 wt % of ethylacetate, which has the following NMR data:

1H-NMR (CDCl3, 300 MHz) 8.58 (ddd, 1H, J=4.8, 1.7, 0.9); 8.19 (dt, 1H,J=7.9, 1.0); 7.8 (td, 1H, J=7.7, 1.8); 7.72 (dd, 1H, J=8.6, 2.3); 7.66(d, 1H, J=2.3); 7.34 (ddd, 1H, J=7.6, 4.8, 1.2); 7.31 (d, 1H, J=8.6);6.87 (dm, 1H, j=1.0) 4.09-4.02 (m, 1H); 3.68 (s, 3H); 2.9-2.7 (m, 4H);2.35 (d 3H, J=1.0), which correspond to the compound of formula (F). Thecalculated molecular weight was 640 g/mol corresponding to a yield 76%.

Example A6

Preparation of3-[(4S)-8-bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-a][1,4]benzodiazepine-4-yl]propionicacid methyl ester of formula (F) using a combination of a catalyticamount TEMPO and hypochlorite as oxidizing agent followed by acidiccyclisation

a) Formation of3-[(S)-7-bromo-2-(2-oxo-propylamino)-5-pyridin-2-yl-3H-1,4-benzodiazepin-3-yl]-propionicacid methyl ester of formula (FK) in ethyl acetate/toluene

230 mg (0.5 mmol) of the compound of formula (E) were dissolved in 1 mlof dichloromethane and cooled to less than 0° C. (in an ice/ethanolbath) giving a yellowish solution. 4.2 mg of sodium hydrogen carbonate(0.05 mmol) and 2.6 mg sodium bromide (0.025 mmol) were added. 0.78 mg(0.005 mmol) of TEMPO was added, immediately followed by 0.33 ml of a2.1 mol/l NaOCl solution (0.7 mmol). The organic layer was colorless andthe aqueous layer yellowish. The reaction mixture was stirred vigorouslyovernight. HPLC showed as main product a ketone and no presence of thecompound of formula (E). The isolated main product showed the followingNMR data:

1H-NMR (CDCl3, 300 MHz) 8.65 (ddd, 1H, J=4.8, 1.8, 0.8); 7.93 (dt, 1H,J=7.9, 1.0); 7.8 (td, 1H, J=7.7, 1.8); 7.52 (dd, 1H, J=8.6, 2.3); 7.41(d, 1H, J=2.3); 7.36 (ddd, 1H, J=7.5, 4.8, 1.2); 7.2 (d, 1H, J=8.8);4.25 (dd, 2H, J=90, 20); 3.71 (s, 3H) 3.36 (m, 1H); 2.85-2.40 (m, 4H);2.21 (s, 3H), corresponding to the compound of formula (FK).

b) Cyclisation into the Compound of Formula (F)

1.83 g (4 mmol) of the compound of formula (FK) was dissolved in 15 mlchloroform. 76 mg (0.4 mmol) p-toluene sulfonic acid was added and themixture was refluxed for 3 days. The reaction mixture was diluted withdichloromethane washed with sodium hydrogen carbonate solution, driedwith magnesium sulphate and evaporated. The isolated main product showedthe following NMR data:

1H-NMR (CDCl3, 300 MHz) 8.58 (ddd, 1H, J=4.8, 1.7, 0.9); 8.19 (dt, 1H,J=7.9, 1.0); 7.8 (td, 1H, J=7.7, 1.8); 7.72 (dd, 1H, J=8.6, 2.3); 7.66(d, 1H, J=2.3); 7.34 (ddd, 1H, J=7.6, 4.8, 1.2); 7.31 (d, 1H, J=8.6);6.87 (dm, 1H, j=1.0) 4.09-4.02 (m, 1H); 3.68 (s, 3H); 2.9-2.7 (m, 4H);2.35 (d 3H, J=1.0), corresponding to the compound of formula (F).

Example A7

Preparation of3-[(4S)-8-bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-a][1,4]benzodiazepine-4-yl]propionicacid methyl ester benzene sulfonate (P) by one-pot cyclization of thecompound of formula (FK) and salt formation

2 g (3.63 mmol) of the compound of formula (FK) were dissolved in 12 mlethyl acetate at room temperature. 0.563 g (3.56 mmol) of benzenesulfonic acid was dissolved in 5.6 ml ethanol and added drop wise over 5minutes to the reaction mixture. Precipitation. After 1 hour the solidwas isolated by filtration, washed with ethyl acetate to give 1.09 goff-white solid, with the following NMR data:

1H-NMR (CDCl3, 300 MHz) 8.60 (ddd, 1H, J=4.8, 1.7, 0.9); 8.20 (dt, 1H,J=7.9, 1.0); 7.9 (m, 2H); 7.8 (m, 2H); 7.53 (d, 1H, J=1.2); 7.47 (d, 1H,J=8.8); 7.44-7.36 (m, 4H); 4.46-4.39 (m, 1H); 3.62 (s, 3H); 3.0-2.6 (m,4H); 2.43 (s, 3H, J=1.0), corresponding to the compound (P). Thechemical purity as determined by HPLC (230 nm) was 99.07% and theoptical purity as determined by HPLC (290 nm) was 99.98%.

Example A8

Preparation of3-[(4S)-8-bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-a][1,4]benzodiazepine-4-yl]propionicacid methyl ester benzene sulfonate (P) from3-[(4S)-8-bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2-a][1,4]benzodiazepine-4-yl]propionicacid methyl ester of formula (F)

The crude compound of formula (F) (783 g residue from Example A5) wasdissolved in ethyl acetate (3.8 l). A solution of benzenesulfonic acid(228 g, 1.44 mol) in ethanol (1.8 l) was added within 50 minutes understirring. The resulting sticky yellow suspension was stirred for another50 minutes. The solid was isolated by filtration, washed with ethylacetate (0.6 l), then dried overnight at 45° C. and 125 mbar in a dryingoven. Yield was 702 g (81%) of a white solid with a chemical purity asdetermined by HPLC (230 nm) was 99.35% and the optical purity asdetermined by HPLC (250 nm) was 99.91%, with the following NMR data:

1H-NMR (CDCl3, 300 MHz) 8.60 (ddd, 1H, J=4.8, 1.7, 0.9); 8.20 (dt, 1H,J=7.9, 1.0); 7.9 (m, 2H); 7.8 (m, 2H); 7.53 (d, 1H, J=1.2); 7.47 (d, 1H,J=8.8); 7.44-7.36 (m, 4H); 4.46-4.39 (m, 1H); 3.62 (s, 3H); 3.0-2.6 (m,4H); 2.43 (s, 3H, J=1.0), corresponding to the compound (P).

What is claimed is:
 1. A salt of a compound of the formula


2. The salt according to claim 1, wherein said salt is a hydrochloridesalt.
 3. A process for preparing a salt of a compound of the formula

wherein R is hydrogen, comprising reacting a compound of the formulawherein R is —C(O)O-tBu with an acid.
 4. The process according to claim3, wherein said acid is hydrochloric acid.
 5. The process according toclaim 3, wherein said salt is a hydrochloride salt.
 6. A process forpreparing a compound of the formula

comprising reacting a compound of the formula

with an acid.
 7. The process according to claim 6, wherein said acid ishydrochloric acid.